Free-piston internal-combustion engines



Aug. 28, 1945. H. STEINER FREE PISTON INTERNAL-COMBUSTION-ENGINE Filed April '22, 1943 2 Sheets-Sheet l ATTORNEYS Aug. 2s, 1945.

H. STEINER FREE P ISTON INTERNAL-COMBUSTION ENGINE Filed April 22, 1943 2 Sheets-Sheet 2 Patented Aug. 28, 1945 FREE-PISTON INTERNAL-COMBUSTION ENGINE Hans Steiner, Winterthur, Switzerland, assigner to Sulzer Freres, Socit Anonyme, Winterthur, Switzerland Application April 22, 1943, Serial No. 484,011 In Switzerland May 28, 1942 (cl. 12s-46) 6 Claims. The invention relates to a free-piston internal combustionengine, with several scavenging-air pipes leading to the internal combustion cylinder and having the scavenging-air currents directed opposite to each other and consists in one or more members being provided to restrict or prevent the passage of scavenging-air from one pipe into another. Preferably at least oneI scavenging-air pipe is provided with one or more non-return through the collecting chambers I2 and I3 and the scavenging-air pipes I4 and I5 to the inlet ports i5 of the internal combustion cylinder I. The internal combustion cylinder I has a fuel valve Il and outlet ports I8 and is connected by means of the power gas pipe I9 to the powergas container 20.

During the inward stroke of the free pistons 4 and 5 the compressor pistons 8 and 9 draw air valves. In addition to the members affecting thc 10 in, which they compress in the ilrst part of the passage of scavenging-air from one pipe into anoutward stroke; after that the compressed air is other on the one hand, a collecting space may be f0rced^0ut of the Cylinders 2 and 3 into the col built into the pipingnear the scavening-air comlecting chambers I2 and I3. In the internal compressor and may have a volume which is almultibu'ston cylinder I towards the end of the outple of the cynnder volume swept by the internal Ward stroke, the outlet ports I8 are opened and combustion piston associated with the comthrough them the combustion gases or DOWeI pressor, on the other hand the pipe connecting gases flow into the container 20. When the presthe space'to the internal combustion cylinder may sure in the internal combustion cylinder has have preferably the same or a smaller cross-secfallen suiliciently far, the inlet ports IG begin to tion than the cross-section of the internal comopen, thereby admitting scavenging air from bustion cylinder. the chambers I2 and I3 into the internal com- In ,contrast to known free-piston engines, parbustion cylinder I. ticularly to those in which the air inlet into the I'he difference in time between the beginning internal combustion cylinder takes place directof the Separate phases of the expulsion of the air ly out of a scavenging-air collecting space surfrom the compressor cylinders and the scavengrounding the internal combustion cylinder on all ing-air entry at the internal combustion cylinsides, the invention has the advantage that it preder on thc one hand, of the outlet phase and of vents disturbances in the scavenging from drops the scavenging phase at the internal combustion in pressure in the internal combustion cylinder y cylinder on the other hand, as necessitated by the and fouling of the air contents through the eX- 39 free-piStOn Operation, makes it DOSSible fOr the haust gases, air columns to oscillate yor for pressure Waves In the drawings examples of constructions acto form in the scavenging-air piping between the cording to the invention are shown diagramoutlet and the inlet, whereby the scavenging of matically. y the internal combustion cylinder I may be inter- Fig. lis a longitudinal section through a freefered with. Also the differentl lengths of the piston engine with collecting chambers on the scavenging-air pipes I4 and I5, necessitated by compressor cylinders. the symmetrical arrangement of the compressors Fig. 2 is a cross-section on the line II-II of 2 and 3 and the one-sided arrangement'of the Fig. 1. inlet ports I6 with respect tothe combustion Fig. 3 illustrates a subdivision of the inlet ports 40 spac of the internal combustion cylinder I, may ofthe air space surrounding the inlet ports of cause such oscillations or pressure waves. the internal combustion cylinder. The device which damps or. prevents the os- Fig. 4 is a longitudinal section through a freecillation of the air column in the scavengingpiston engine with a chamber at the internal air pipes I4 and I5 or the occurrence of a prescombustion cylinder. 45 sure wave, consists in Fig. 1 on the one hand of Fig. 5 isalongitudinal sectional view througha the collecting chambers I2 and I3 arranged in free-piston engine generally similar to that shown the pipes I4 and I5 close to the compressors2 in Fig. 4. and 3, the volumeof each collecting chamber The free-piston engine in Fig. I has an inbeing two, three or more times that of the volume ternal combustion cylinder I and two compressor ofthe internal combustion cylinder swept by the cylinders 2 and 3 in which the free pistons 4 and pistons 6 and 1 associated with the compressors 5 work with the internal combustion pistons 6 2 and 3 respectively, and on the other hand of and 1 and the compressor pistons 8 and 9. 'I'he the pipes I4 and I5 connecting the chambers I2 compressor cylinders 2 and 3 have suction and and I3 to the internal combustion cylinder I, the 1 delivery valves I0 and II and are connected 55 cross-section of these pipes being preferably considerably less than or exactly the same size as the cross-section of the intern-al combustion cylinder I. In special cases, however, the pipes I4 and I5 may also have a cross-section greater than that of the internal combustion cylinder I.

Since the collecting chambers I2 and I3 are in immediate proximity to the delivery valves II, they prevent oscillation occurring during the pressure stroke of the compressors 2 and 3, Whilst tne greater speed oi the air in pipes I4 and I5, in consequence of their small cross-section, prevents oscillation of the air column or a pressure wave occurring in it when that, the pipes I4 and i5 are shut ofrfrom the space 22 surrounding the inlet ports I6 by means of the non-return valves 2| (Figs. 1 and 2) so that any oscillation oi' the power gases in the container occurring during the outlet phase cannot adversely affect the scavenging operation through a back-now of air or a pressure wavein the pipes I4 and I5 in a direction contrary to the scavenging-air iiow.

The air speed in the scavenging-air pipes I4 and I5 caused by arranging the collecting chambers I2 and I3 close to the compressor cylinders 2 and 3, brings, in addition to that, the advantage that favourable conditions are obtained in the internal combustion cylinder I from the end of the scavenging phase untilV the closing of the scavenging ports I6 in consequence of the kinetic energy of the air columns in these pipes.

The different lengths of the pipes I4 and I5, when the compressor pistons 8 and S begin simultaneously to force air into the receivers I2 and I3, may also cause different pressure conditions at different times at the outletI of the pipes I4 and I5 into the space 22. In order to prevent air fiowing through from pipe I4 into pipe I5, or-

vice versa because of such diierences in pressure, the space 22 in Fig. 3 is subdivided into two spaces 24 and 25 by means of a partition wall .23, instead of having the non-return valves 2| as in Fig. 2.

The scavenging-air pipes I4 and I5 in Fig. 4 are connected direct to the compressor cylinders 2 and 3, omitting the chambers I2 and I3 as in Fig. l. Their outlet ends 26 `are arranged with respect to each other at' the container 2l in such a way that the currents of scavenging-air flowing from them are directed opposite to each other. For damping pressure waves or checking air flowing back into pipes I4 and I5, special throttling nozzles 29 are built into the pipes I4 and I5. The throttling nozzles 29 may also be designed in some -other manner. used instead of the non-return valves or together with them.

The free-piston engine shown in Fig. 5 is similar to that shown in Fig. 4 except that the scavenging-air pipes I4 and I5 are of greater diam- 'I'hey may be scavenging. In addition to aseaeac eter than the internal combustion cylinder I and their outlet ends are Vprovided with nonreturn valves 30 in order to avoid possible troubles in consequence of the two pipes being of different lengths.

In each of Figs. l, 4 and 5 a synchronizing mechanism comprising two-arm lever 3l and connecting rod 32 connected to one arm of` said lever and free-stroke piston 6 and a connecting rod 33 connected to the other end of said lever and free-stroke piston 1 Vis provided for assuring countermovement of the pistons.

I claim:

1. A free-piston internal combustion engine. with several scavenging-air pipes leading -to circumferentially spaced intake -ports of the internal combustion cylinder and having the scavenging-air current directed opposite to each other in the cylinder, which comprises means for causing the air to ow from each of the several pipes through the inlet ports leading into the cylinder and for at least restricting the scavenging-air from flowing from one pipe into another.

2. A free-piston engine according to claim 1 which comprises a non-return valve in at least one of the pipes.

3. A free-piston engine according to claim 1 which comprises at least one throttling nozzle in each pipe to restrict the iiow of air from one pipe into another.

4. A free-piston engine according to claim l which comprises a compressor piston driven by each free-piston to compress the scavenging-air, a collecting space connected to each pipe for receiving the air from each compressor, the diameter of the pipes being not greater than the di ameter of the engine cylinder.

5. A free-piston internal combustion engine with at least two scavenging-air pipes which'are connected to the inlet ports of the internal combustion cylinder arranged opposite to each other,

which comprises wall-means forming a space surrounding the cylinder and the intake ports, a partition dividing the space into two parts, a scavenging-air pipe being connected to each part of the space, whereby air does not flow from one pipe into another, the intake ports being so arranged in thecylinder that ports in one space are diametrically opposite ports in the other space.

6. A free-piston engine according to claim l which comprises a compressor piston driven by each free piston to compress the scavenging-air, aI collecting space connected to each pipe for receiving the air for each compressor, the volume of the collecting space being not less than twice the volume of the cylinder swept by the engine piston, the diameter of the pipes being not greater than the diameter of the engine cylinders.

HANS STEINER. 

